Oxidative condensation of alkyl aromatic hydrocarbons and of nuclearly chlorinated alkyl aromatic hydrocarbons



Patented Oct. 14, 195 2 OFFICE OXIDATIVE CONDENSATION OF ALKYL AROMATICHYDROCARBONS AND OF NUCLEAR-LY CHLORINATED ALKYL AROMA'IIC HYDROCARBONSHerman Pines, Bruno Kvetinskas, and Vladimir N. Ipatieff, Chicago, 111.,assignors to Universal Oil Products Company, Chicago, 111., acorporation of Delaware N Drawing.

Application March 26, 1949,

Serial No. 83,774

9 Claims.

This invention relates to a process for oxidizing alkyl aromaticcompounds and particularly for oxidizing a member of the groupconsisting of alkyl aromatic hydrocarbons and nuclearly chlorinatedalkyl aromatic hydrocarbons to effect the formation of a diarylalkane orof a nuclearly chlorinated diarylalkane.

An object of this invention is to produce a diarylalkane hydrocarbon.

Another object of this invention is to produce a nuclearly chlorinateddiarylalkane.

One specific embodiment of this invention relates to a process forproducing a member of the group consisting of a diarylalkane and anuclearly chlorinated diarylalkane which comprises reacting in thepresence of at least one member of the group consisting of magnesium andaluminum, a gas containing free oxygen and a member of the groupconsisting of an aromatic hydrocarbon and a nuclearly chlorinatedaromatic hydrocarbon each having an alkyl group containing at least oneand not more than two hydrogen atoms combined with the carbon atomattached to the aromatic ring.

, Another embodiment of this invention relates to a process forproducing a diphenylalkane which comprises reacting in the presence ofaluminum a gas containing free oxygen and a benzene hydrocarbon havingan alkyl group of at least two carbon atoms and containing at least onehydrogen atom combined with the carbon atom attached to the benzenering.

A further embodiment of this invention relates to a process forproducing a nuclearly chlorinated diphenylalkane which comprisesreacting in the presence of aluminum a gas containing free oxygen and anuclearly chlorinated alkyl benzene hydrocarbon in which said alkylgroup contains at least two carbon atoms and at least one hydrogen atomcombined with the carbon atom attached to the benzene ring.

We have found that the treatment in the presence of at least one metalof the group consisting of magnesium and aluminum of certain alkylaromatic hydrocarbons and nuclearly chlorinated alkyl aromatichydrocarbons with air, oxygen, or oxygen in admixture with an inert gasor mixture of inert gases results inthe removal of hydrogen from saidalkyl aromatic compounds and the production of an aromatic hydrocarbonof higher molecular weight including a diarylalkane and a di(chloroaryl)alkane,

The aromatic compounds suitable for use in this process include alkylaromatic hydrocarbons and nuclearly chlorinated alkyl aromatichydrocarbons each containing an alkyl group of at least two carbon atomsand containing at least one hydrogen atom combined with the carbon atomof said alkyl group attached to the arc.- matic ring. While the aromaticring ofsaid starting material is preferably a benzene ring, it may alsobe a polycyclic ring including at least one benzene ring such as anaphthalene ring, a tetralin ring, or other polycyclic aromatic.hydrocarbon ring. Accordingly, aromatic. hydrocarbons which may be soused as starting materials in our process include ethylbenzene, cumene,cymene, propylbenzene, butylbenzene, sec.-buty1- benzene,isobutylbenzene, and higher boiling monoalkyl, dialkyl, and otherpolyalkyl benzenes in which the carbon atom of an alkyl group attachedto the benzene ring is also attached to one but not more than twohydrogen atoms. Nuclearly chlorinated alkyl aromatic hydrocarbons havingan alkyl group containing at least one and not more than two hydrogenatoms bound to the carbon atom attached to the aromatic ring are alsosuitable starting materials for producing a di(chlor0aryl)a1kane.

We have found that the above indicated alkyl aromatic hydrocarbons andnuclearly chlorinated oxygen are then contacted with the liquidaromolecular proportions of paracymene condensed with or reacted witheach other to form 2,3-dimethyl-2,3-dito1yl butane and water asillustrated by the following equation:

The above indicated reaction may also be applied to other alkyl aromatichydrocarbons such as dialkyl aromatic hydrocarbons. Such a reaction isillustrated by the following equation in which R1 and R2 represent alkylgroups each separately and independently containing at least two carbonatoms and generally containing from about 2 to about 4 carbon atoms andsaid aromatic hydrocarbons containing less than four of said R groupsper molecule:

This oxidative condensation of an aromatic hydrocarbon such asparacymene is accompanied by the formation of oxygenated compounds suchas carbinols, ketones, and higher boiling products in addition to thediarylalkane formed as indicated in the foregoing equations.

Similarly, the oxidation treatment of parachloroisopropylbenzene(sometimes referred to as parachlorocymene) is carried out in thepresence of aluminum turnings or magnesium turnings which serve ascondensation catalyst. In the presence of the aluminum turnings a yieldof 7% per pass is obtained of the condensation productherein referred toas 2,3-dimethyl-2,3-pchlorophenylbutane.

This process may be carried out in either batch orcontinuous types ofoperation. In a typical batch-type operation, the aromatic hydrocarbon,metallic aluminum (generally in the form of turnings) sometimes also abase such as sodium carbonate, potassium carbonate, etc., are placed ina reactor heated to a temperature of from about 100 to about 250 C. andmaintained at a pressure sufficient to keep a substantial proportion ofthe hydrocarbons and chlorinated aromatic hydrocarbons in liquid phasewhile air or another gas containing free oxygen is passed therethrough.The use of a basic material and also at least one metal selected fromthe members of the group consisting of magnesium and aluminum promotesthe formation of a high yield of diarylalkane or nuclearly chlorinateddiarylalkane depending upon the type of the charging stock charged tothe process.

In continuous operation, an alkyl aromatic hydrocarbon or nuclearlychlorinated alkyl aromatic hydrocarbon of the type indicated hereinand-air or oxygen or some other oxygen containing gas are passed througha heated reactor containing at least one of the metals selected from themembers of the group consisting of magnesium and aluminum and havingatomic numbers 12 and 13 and the resultant reaction products are thenrecovered and separated into the condensation products and unconvertedstarting macarbonate.

terials, the latter being suitable for further treatment in the process.

The following examples are given to illustrate the type of resultsobtained in this process although the data presented are not introducedwith the intention of restricting unduly the broad scope of theinvention.

EMMPLE I Batch-type runs were made by placing an aromatic hydrocarbon ina flask and heating therein to the desired temperature while air wasbubbled into the hydrocarbon through a how meter. At the end of the runthe current of air was shut off, the peroxide number of the product wasdetermined and the product was distilled without further treatment forin no case was the peroxide number dangerouly high. The unreactedhydrocarbon was distilled off at atmospheric pressure, the remainingproduct was cooled and filtered with suction to remove crystallineproducts and the liquid filtrate was fractionally distilled at reducedpressure. Some of the fractions were examined by infra-red absorptionmethods to determine the amount of ketone, alcohol, and diaryl alkanespresent. Thus on heating p-cymene at 173 C. and passing air through theheated hydrocarbon at a rate of 2.8 liters per hour for 20 hours, atotal of 32 grams of higher boiling product was obtained containing 50%of p-methylacetophenone, 27% of 2,3-dimethy1-2,3-ditoly1butane, whichmay also be called dicymene, and 23% of an intermediate fractioncontaining some dicymene.

EXAMPLE II In order to increase the yield of dicymene, other oxidationruns were made by treating p-cymene with air in the presence of metallicaluminum. The aluminum contacting material in an amount of about 400 cc.was placed in the reaction flask into which was introduced 600 grams ofcymene. The latter was heated to a reflux temperature under a refluxcondenser and a stream of air was passed through the heated hydrocarbonat a rate of 12 liters per hour. It was found that the presence of thealuminum packing material increased the yield of oxidation productsobtained from p-cymene. I i

In another run the oxidation treatment of pcymene was carried out for atime of 18 hours in the presence of aluminum turnings and potassium Theresults obtained in these two runs, that is, in the presence of aluminumturnings, and in a mixture of aluminum turnings and potassium carbonateare summarized by the following table:

Table I 1 p-Oymene, g 600 I 600 Aluminum turnings, grams. 209 2-14Potassium Carbonate, grams. None E 20 Air rate, liters/hr 12 4 12Temperature, C 171 172 Time on stream, hrs l l8 18 Results: l

Reacted product, weight percent n 13 i 17 Composition of reactedproducts, pcrccnt i lietoncs and Carbinols .Q. .I i 3:] Dairylalkancs J.7 33 27 7 Bottoms 1 Composition: 2,3-dimcthyl2,3 li(p-tolyDbutmc.

From the above indicated results, it is evident that the production ofdicymene was greater in the presence of both aluminum turnings andpotassium carbonate than in the presence of aluminum turnings alone.That is, the yield of di-p-cymene was increased from 27 to 33% and theyield of ketone-carbinol fraction was also increased from 28 to 35%while the amount of higher boiling products (indicated in the table asbottoms) was reduced from 45 to 29%.

EXAMPLE I11 By following essentially the same procedure as that inExample II, 12 liters of air per hour were passed through 600 grams ofp-cymene maintained at a temperatureof 172 C. during a time of 18 hours.The p-cymene being treated was in contact with 165 grams (400 cc.) ofmagnesium turnings and also 20 grams of potassium carbonate. At the endof this treatment, the liquid oxidation product had a peroxide number of17.3, a refractive index 12 of 1.4968. During this treatment there wereformed 5.4 cc.'oi water and 76.3 grams of reaction product boilinghigher than p-cymene. The reaction product so obtained boiling higherthan p-cymene contained 4.2% of organic acids, 39% of a mixtureofpmethyl-p-tolyl carbinol, 16.1% of higher boiling liquids, 28% of2,3dimethyl-2,3-di-p-to1ylbutane, and 12.7% of residue."

EXAMPLEIV Following the procedures of Examples II and III, 600 grams ofcumene was heated to a tem-.

Table II Experiment No 6 8 Aromatic charged:

Kind Cumene grams 600 Contact medium:

Kind

Soft glass 8 Air rate, liters/hr... Temperature, 0.. x I Time on stream,hr Results:

Peroxide No m. oi product Total water formed, cc... Reacted product:

grams weight percent 1 Composition of unreacted product (excluding unreagted charged):

Higher boiling liquid Diarylalkane 3 Bottoms Analysis of Ketone-carbinolfraction, percent:

in (me 5 Carbinol 4 1 The weight of product taken for distillation afterwashing and drying is used for this calculation ll)l'he1n cumene ischarged it is acctophenone+dimethylphenyl car 1110 3 When cumene ischarged it is 2,3-dimethyl-2,3diphenylbutane.

In the presence of the soft glass rings, the reaction product contained10.4% by weight of reacted material which consisted of 82.6% of aketone-carbinol fraction, 9.1% of dicumene and 8.0% of higher boilingmaterial. The presence of aluminum turnings in the reaction zonemarkedly increased the yield of the dicumene and decreased the yield ofthe ketone-carbinol fraction. The amount of reacted material in theproduct was 10.2%. The reaction products boiling higher than cumeneconsisted of 60.9% 01 ketonecarbinol fraction, 26.9% of dicumene and12.2% higher boiling liquid and bottoms when aluminum turnings werepresent in the reaction zone.

When the metals magnesium and aluminum were used as contacting media inthe oxidation of cumene and p-cymene, the yield of diarylalkane and highboiling products was increased over that obtained in the absence of themetal whil the ketone-carbinol yield was increased. The addition ofpotassium carbonate to the metal resulted in the formation of a cleaneroxidation product which contained smaller amounts of high boilingresidue but larger amounts of ketone-carbinol fraction and also largeramounts of diarylalkanes.

EXAMPLE V s-Butylbenzene was reacted with air for 18 hours at 169 in thepresence of aluminum turnings and potassium carbonate. The productcontained 12.9 weight per cent of material boiling higher than thecharge, of this, 0.7% was acid, 53% boiled in the ketone-carbinol range,17.3% was a crystalline dimer of s-butylbenzene, 21.4% high boilingliquid, and 7.6% remained as bottoms. The structure of the crystallinedimer is that of 3,4-dimethyl-3,4-diphenylhexane. Recrystallized fromethanol it melted at 97-98.

EXAMPLE VI p-Chlorocumene was reacted for 18 hours with air at 171 inthe presence of potassium carbinate using aluminum turnings as a contactmaterial. in one case and glass rings in another case. The weight percent of product boiling higher than the charge was 15.4 when aluminumturnings were employed and 26.8 when glass rings were used. On recyclebasis, when aluminum turnings were used, the product consisted of 1.9%acids. 70.8% ketone-carbinol fraction, 12.7% higher boiling liquid, 6.9%di-p-chlorocumene, and 7.7% resinous bottoms; and when glass rings wereused. it consisted of 2.4% acids, 85.7% ketone-carbinol fraction, 5.4%higher boiling liquid, 1.2% di-pchloroeumene and 5.3% resinous bottoms.The yield of dimer from p-chlorocumene was not nearly as high as thatobtained from p-cymene or cumene but the efiect of the aluminum is inthe same direction, that is, it increased the yield of dimer. Thestructure of the crystalline di-pchloroeumene is indicated as2,3-di-p-chlorophenyl-2,3 -dimethylbutane. Recrystallized from absoluteethanol, it melted at 166-167".

We claim as our invention:

1. A process for producing a member of the group consisting of adiarylallrane and a nuclearly chlorinated diarylalkane from an aromaticcompound of the group consisting of an aromatic hydrocarbon and anuclearly chlorinated aromatic hydrocarbon each having an alkyl groupcontaining at least one and not more than two hydrogen atoms combinedwith the carbon atom attached to the aromatic ring, which comprisessubjecting said aromatic compound to oxidative condensation by reactingthe same with free oxygen at a temperature of from about to about 250 C.in the presence of at least one metal of the group consisting ofaluminum and magnesium.

2. A process for producing a diphenylalkane which comprises reacting ata temperature of from about 100 to about 250 C. in the presence ofaluminum a gas containing free oxygen and an aromatic hydrocarbon havingan alkyl group of at least two carbon atoms and containing at least onehydrogen atom combined with the carbon atom attached to the benzenering.

3. A process for'producing a nuclearly chlorinated diphenylalkane whichcomprises reacting at a. temperature of from about 100 to about 250 C.in the presence of aluminum a .gas containing free oxygen and anuclearly chlorinated alkyl aromatic hydrocarbon in which said alkylgroup contains at least two carbon atoms and at least one hydrogen atomcombined with the carbon atom attached to the benzene ring.

4. A process for producing a diphenyl alkane which comprises reacting agas containing free oxygen and a benzene hydrocarbon having an alkylgroup of at least two carbon atoms and containing at least one hydrogenatom combined with the carbon atom attached to the benzene ring at atemperature of from about 100 to about 250 C. in the presence ofaluminum.

5. A process for producing a diphenyl alkane which comprises reactingair and a benzene hydrocarbon having an alkyl group of at least twocarbon atoms and containing at least one hydrogen atom combined with thecarbon atom attached to the benzene ring at a temperature of from about125 to about 200 C. in the presence of aluminum.

6. A process for producing a diphenyl alkane which comprises reacting agas containing free oxygen and a benzene hydrocarbon having an alkylgroup of at least two carbon atoms and containing at least one hydrogenatom combined with the carbon atom attached to the benzene ring at atemperature of from about 100 to about 250 C. in the presence ofmagnesium.

7. A process for producing a diphenyl alkane which comprises reactingair and a benzene hydrocarbon having an alkyl group of at least twocarbon atoms and containing at least one hydrogen atom combined with thecarbon atom attached to the benzene ring at a temperature of from about125 to about 200 C. in the presence of magnesium.

8. A process for producing a nuclearly chlorinated diphenyl alkane whichcomprises reacting a gas containing free oxygen and a nuclearlychlorinated alkyl benzene hydrocarbon in which said alkyl group containsat least two carbon atoms and atleast one hydrogen atom combined withthe carbon atom attached to the benzene ring at a temperature of fromabout to about 250 C. in the presence of aluminum.

9. A process for producing a nuclearly chlorinated diphenyl alkane whichcomprises reacting airand a nuclearly chlorinated alkyl benzenehydrocarbon in which said alkyl group contains at least two carbon atomsand at least one hydrogen atom combined with the carbon atom attached tothe benzene ring at a temperature of from about 'to about 200 C. in thepresence of aluminum.

HERMAN PINES. BRUNO KVE'I'INSKAS. VLADIMIR N. IPATIEFF.

Berkman et a1.: Catalysis, page 808 (1940).

Groggins: Unit Processes in Organic Synthesis, page 480 (1947), 3rdedition, McGraw-Hill Publishing Co., New York, N. Y.

Number

1. THE PROCESS FOR PRODUCING A MEMBER OF THE GROUP CONSISTING OF ADIARYLALKANE AND A NUCLEARLY CHLORINATED DIARYLALKANE FROM AN AROMATICCOMPOUND OF THE GROUP CONSISTING OF AN AROMATIC HYDROCARBON AND ANUCLEARLY CHLORINATED AROMATIC HYDROCARBON EACH HAVING AN ALKYL GROUPCONTAINING AT LEAST ONE AND NOT MORE THAN TWO HYDROGEN ATOMS COMBINEDWITH THE CARBON ATOM ATTACHED TO THE AROMATIC RING, WHICH COMPRISESSUBJECTING SAID AROMATIC COMPOUND TO OXIDATIVE CONDENSATION BY REACTINGTHE SAME WITH FREE OXYGEN AT A TEMPERATURE OF FROM ABOUT 100* TO ABOUT250* C. IN THE PRESENCE OF AT LEAST ONE METAL OF THE GROUP CONSISTING OFALUMINUM AND MAGNESIUM.